Rectifying system



Jan- 11, 1949. H. KLEMPERER -ET AL 2,458,516

RECTIFYING SYSTEM Filed Dec. 5, 1945 25/?0 AXIS 2 25/20 AXIS F 3 5 2920 Am F7014.

TIME+ l I N F70. 5 j i ZERO WVE'NTORS 3 HANS KLEMPERER 1 M lL/AMFH .TLEY

Mi 2M6}! Any Pat'ented Jan. 11, 1949 RECTIFYING SYSTEM Hans Klemperer, Belmont, and William F. Huntley, Lowell, Mass., assignors to Raytheon Mann. facturing Company, Newton, Masa, a eorpora tion of Delaware Application December 5, 1945, Serial No. 632,950

5 Claims. (01. 175-363) This invention relates to rectifying systems, and more particularly to an arrangement for delivering smooth rectified current from a single phase alternating current source.

An object of the invention is to provide such a system in which the direct current output has less ripple or deviation from the ideal square output wave than that resulting from the conventional prior art systems, and which therefore requires less filtering in order to produce the desired steady or uniiuctuating direct current for utilization in a load device.

Another object of the invention is to provide a rectifying system of the above character in which no condensers or other external energy-storage means are used.

A further object is to provide such a system which is relatively simple to construct and easy to maintain. 1

The foregoing and other obj'ectsof the invention will be best understood from the following description of an exemplification thereof, ref-= erence being bad to the accompanying drawing, wherein:

Fig. 1 is a diagrammatic representation of a circuit embodying the novel system; and

Figs. 2, 3, 4, and 5 represent various voltages and fluxes flowing in the novel system.

In Fig. 1 there is represented a transformer core I of the three-phase type, having three legs 2, 3, and ll. Around these legs are placed, respectively, primary winding 5, secondary winding 6, and tertiary winding l, windings 6 and lbeing center-tapped at it and i9, respectively. Winding 5 is connected to a source of alternating current 8 and serves as the exciting winding. The two end terminals of secondary winding 6 are connected to the respective anodes ii of a fullwave thermionic rectifier tube I0. Tube Ill contains a cathode II, which is raised to emission temperature by any suitable heater. The two end terminals of tertiary winding 1 are connected to the respective anodes l2 of a second full-wave thermionic rectifier tube l3. Tube I3 also contains an indirectly-heated cathode l4. Cathodes II and ll of tubes l and I3 are connected together to serve as the positive lead It for the direct current output of the system, While midtap l8 of winding 6 and midtap 19 of winding 1 are connected together in a similar manner to serve as the negative lead I! for the direct current output. Load device I is connected across leads i6 and H. The load is here represented as a resistor but may be any type of load for which a D. C.

- to winding 5 from source supply is desired. The voltages'appearing across windings 6 and 'l are rectified and combined or mixed by the circuit including the two rectiflers ill and I3, and are then applied to the load.

Leg 3 of transformer l is spaced from the main body of the transformer core, at a point adjacent its end, to provide an airgap 2d. Leg t of transformer i is made of smaller cross-sectiona1 area than the remainder of the core, so that this leg will become saturated or willreach the saturation point, in regard to magnetic a substantial time before the primary flux reaches its maximum value.

Legs 3 and 4 therefore provide, in effect, two flux paths in parallel across the magnetomotive force represented by the current from source 2 flowing through primary winding time or" these two paths, that including leg 3 is of high reluctance, due to the presence of airgap which is effectively in series with this flux path. The other of these two paths, that including leg l, is initially of lower reluctance, due to the continuous path through the ferromagnetic material of this leg, but, as this leg approaches saturation, it acts in effect as a very high reluctance flux path because even though the primary or exciting flux continues to increase, the flux through saturated leg l remains substantially at a constant value, which is that at the point of saturation.

The above relations of fluxes ar explained more fully in connection with Figs. 2-3. In Fig. 2, curve E5 represents the sinusoidal voltage applied Curve oz, in the same figure, represents the primary alternating magnetic flux which results from the magnetomotive force of current from the source flowing through primary winding 5. Under ordinary conditions, as is well lmown, this flux is also sinusoidal in wave form and is ninety degrees out of phase with the voltage across the winding, and it is so represented in Fig. 2. In Fig. 2, the dashed horizontal lines above and below the zero axis represent the values of flux at which leg 4 becomes saturated.

In Fig. 3, curve (#3 represents the cyclical variation of magnetic flux in leg 3 of the transformer, while curve e4 represents the cyclical variation of magnetic flux in leg 4 of the transformer. Since the flux paths including legs 3 and 4 are effectively in parallel across the source of primary magnetic flux, as stated above, the sum of the instantaneous flux values of curves 3 and 4 will at all times be equal to the primary flux o2, neglecting the-slight leakage fluxes which naturally occur. Starting at the zero point A of prireluctance than leg 4, the original rate of changeof flux in leg 4 will. be greater than that in leg 3, as shown between points D and E in Fig. 3. As point B is reached on the primary flux curve ca which point represents the value of fiux necessary to saturate leg 4, curve begins to flatten out rather abruptly, due to its effectively in creased reluctance, as shown at point E in Fig. 3. Since the total primary flux 2 must equal the sum 01 secondary flux or and tertiary fiux c4, and since flux m is now tending to remain at a. fixed value, due to saturation or leg 4, the flux in leg 8 now begins to increase more rapidly, as shown adjacent point E in Fig. 3. Between points 3 and C, as the primary iiux 2 continues to increase slnusoidally, secondary flux or also in-= creases substantially sinusoidally, as shown between points E and F in Fig. 3, while, due to Saturation of leg 8, tertiary flux c4 remains substantially at a fixed value, increasing only very slight- Iiy if at all. As primary flux or decreases sinusoidally from C to G, secondary flux a also decreases substantially sinusoidally fromF toJ, while tertiary flux 4 decreases only very slightly, if at all, because leg 4 is still saturated. When oint G is reached in the sinusoidal cyclical decrease of primary flux or, the saturation value of flux for leg 4 is again reached but in the downward direction, so that tertiary flux 54 now begins to decrease rather rapidly, as shown at point J in Fig. 3. Also, due to the now decreased reluctance of leg 4 as compared with leg 3, the rate of change of secondary flux cs begins to decrease, so that curve ca tends to flatten out somewhat at this point, as seen in Fig. 3. Between points G and H on primary flux curve or, secondary flux or and tertiary flux or both decrease toward zero, as shown between joints J and K in Fig. 3, curve 4 now changing at a much more rapid rate than curve 53, as explained above.

The variations of secondary flux 953 and of tertiary flux o4 during the next, or negative, halfcycle of primary flux or are exactly similar to those just described for a positive half-cycle of primary flux, but are in the opposite direction from the zero axis, as shown in Fig. 3, so that the curves 3 and 4 areof a periodic symmetrical character, the periods being the same as the half-cycles of primary flux on.

Fig. 4 represents the voltages induced in windings 8 and 1, due tmtransformer action, as a result of the flux changes in legs 3 and 4 which have been described. In this figure, curve Es represents the voltage induced in secondary winding 6 while curve E1 represents the voltage induced in tertiary winding 1. Between points D and E,

before leg 4 becomes saturated, the flux in leg 3 is changing relatively slowly, as stated above, so that the voltage E0 induced in winding 6 is correspondingly low, but is greater than zero, as shown at point M in Fig. 4. As leg 4 becomes saturated, the rate of change of flux in leg 3 increases, so that the induced voltage Es rises toward a maximum at point N or at point E of the flux curve. As flux S3 approaches a maximum at point F, its rate 01' change decreases so that induced voltage Es decreases toward zero and passes through a value of zero at point P, or when flux curve oz has a slope of zero .at point F. As flux o: decreases from point B, induced voltage Es increases from zero but in a-negative direction, reaching a maximum negative value substantially at point J of flux curve (#3. Beyond point J the rate of change of secondary flux s has decreased rather abruptly, so that induced voltage Ea also decreases. As curve 3 approaches a zero value in the vicinity of point K, induced voltage Es continues to decrease until, substantially at point K, a minimum rate of change of flux ca is reached and a minimum induced voltage E0 is also reached. This minimum value of induced voltage is not zero, however, because in this region the rate of change of flux 3 never drops to zero. As the rate of change of flux or increases beyond point X, induced voltage Es again increases toward a maximum negative value, which it reaches substantially at point L of the flux curve, as described above for a maximum positive value at point N, again reaching a value or zero when flux curve o3 reaches its maximum negative value. The above-described variation of voltage induced in winding 6 is repeated periodically. It will therefore be seen that, between maximum positive and maximum negative points of flux curve 4:3, or of primary fiux 2, a voltage wave having two humps or lobes with a valley or depression between is induced in winding a; this wave may be considered to be a mixture of the fundamental frequency of source ll and of odd harmonics of. said fundamental.

The voltage induced in tertiary winding ll will have a high value at point D of curve 4, since at this point, as stated above, the rate of change of flux in leg 5 is relatively high. Between points D and E of flux curve 4, as the saturation point of leg 51 is being approached, the rate of change of flux in leg fl is decreasing, so that induced voltage E1 also decreases. When leg c becomes saturated, at or near point E in Fig. 3, the flux in said leg no longer increases, but remains substantially constant, increasing only extremely slightly if at all; therefore induced voltage E7 drops to substantially zero. Voltage E7 remains substantially at zero until tertiary flux 4 begins to decrease as a result of primary fiux cg reaching the saturation value (of leg Q) on its downward trend. When tertiary flux 4n begins to decrease, which it does at a relatively rapid rate, induced voltage E1 begins to increase, in a negative direction; it increases until point K on the flux curve is reached, at which time it again begins to decrease as leg 4 approaches saturation in a negative direction. The above-described variation of voltage induced in winding l is repeated periodically. It will therefore be apparent that, between maximum positive and negative points of primary flux its, a voltage having the form of a single peaked impulse or wave is induced in winding I, the peak occurring in the vicinity of the zero value of qbz.

It will therefore be seen that the peak of curve E1 occurs during the valley of the double humped wave Es. Ii, therefore, the waves E6 and E: are combined or mixed, the peak of E7 will fill in the valleys of curve Es, giving a combined wave which has a relatively flattened top and is closer to a square wave than the sinusoidal impulses produced by other rectifying systems. The output of this system therefore has less ripple than that produced in other systems. The waves E6 and E1 are combined, or mixed, and rectified in the circuit including rectiflers I0 and l 3, as stated above.

Fig. 5 depicts, by means of curve E15, the voltage appearing across load i5. This i a threehumped, substantially square wave, or a series of substantially square-wave impulses, entirely on the positive side of the zero axis, which results from combining or superposing and rectifying, in a full-wave manner, the voltages Ea and E7 induced in windings 6 and 7, respectively. By means of the full-wave rectification, the negative portions of both waves, E6 and E7, are reversed in polarity and appear on the positive side of the zero axis in Fig. 5.

The invention is not limited to the particular details described above as many equivalents will suggest themselves to those skilled in the art. For example, the rectifying tubes which are used may be of any convenient type; or the rectificrs may be 01 the dry type. The transformer used may be of any convenient type, modified in accordance with the teachings of the invention. it is accordingly desired that the appended claims b given a broad interpretationcommensurate with the scope of the invention within the art.

What is claimed is: v

. 1. A rectifying system comprising a threelegged transformer core with a primary winding around one leg, a secondary winding around a second leg, and a tertiary winding around the third leg, a source of alternating current connected to said primary winding, saidsecond leg being adapted to produce in said secondary winding by transformer action from said source a doublelobed voltage wave with a depression between said lobes, said third leg being adapted to produce in said tertiary winding by transformer action from said source a peaked induced voltage wave, the peak of said last-mentioned wave occurring in time phase with the depression or said first-mentioned wave, and means for mixing and rectifying said waves. V

2. A rectifying system comprising a transformer core having three legs and a plurality of windings, one winding being wound around each leg, one leg having an airgap included therein and another leg being of reduced cross-sectional area relative to the remainder oi the core, a source of alternating current connected to one of said windings, two rectifying devices, means for connecting the windings associated with said one leg and said other leg in circuit with said rectifying devices to combine and rectify the voltages induced in said last-named windings, and a load device connected to be supplied with the combined and rectified voltages.

3. A rectifying system comprising a transformer core having three legs, a winding around one of said legs, separate windings around each of the other two legs, a. source 01' alternating current connected across said one winding, two full-wave rectiflers, the two remaining windings of said transformer being connected together through said rectiflers in such a manner as to combine and rectify the voltages induced in said remaining windings from said one winding due'to'transtormor action, one of said other legs having an airgap included therein, said airgap being in series with the flux path through the same leg, the other of said other legs being constructed and arranged to become saturated during increase of flux produced by said one winding, whereby a doublelobed voltage wave is induced in the winding associated with said one of said other less, and whereby a peaked voltage wave is induced in the winding associated with the second. of said other legs, the peak of said second wave occurring between the lobes of said first wave, the combination of said two voltage waves when rectified producing a substantially flattened-top output wave.

4. A rectifying system comprising a transfonm or core having three legs, a separate winding around each leg to constitute primary, secondary, and tertiary windings, a source otaiternatihg eurrent connected to the ends of said primary winding, center taps on both the secondary and text ary windings, the leg carrying the primary windings being continuous, one of the remaining legs of the core being discontinuous to provide an airgap and the other of the remaining legs being of reduced cross-sectional area relative to the core body, two full-wave thermionic rectifiers each having a fair of anodes and a cathode, a load device, means connecting said center taps together and to one terminal of the load device, means connecting said two cathodes together and to the other terminal of i the load device, means connecting each end of said secondary winding to a corresponding anode of one of said rectifiers, and means connecting each end of said tertiary winding to a corresponding anode of the other rectifier.

, 5. A rectifying system comprising a transformer core having first, second, and third legs, a separate coil wound around each of said legs, means for energizing a first of the coils with alternating current, said second leg being constructed and arranged to produce a double-humped effect in the voltage induced in the coil wound therearound, said third leg being constructed and arranged to produce a peaked efiect in the voltage induced in the coil wound therearound, means for combining and rectifying the induced voltages to produce a substantially flattened-top voltage output, and load means connected to be energized by said out- HANS KLEMPERER. WILLIAM F. HUNTLEY.

REFERENCES CITED UNITED STATES PATENTS Name Date Bediord May 22, 1984 Number 

